Rheum rhabarbarum aka Garden Rhubarb

Rheum rhabarbarum is a large perennial in the Polygonaceae family. Its native range spans southern Siberia to northern and central China. It grows in temperate regions and is known as rhubarb. The RHS also calls it wavy-leaved rhubarb. This species may have helped give rise to culinary rhubarb hybrids. Garden plants reach about 3.3–4.9 feet [1–1.5 metres] tall and wide. They take two to five years to reach full size.

The plant loses its leaves and rests as a short crown through winter. Fresh leaves form a basal clump in spring. Their dark green blades range from triangular to heart-shaped. Deep waves run along their edges. Individual leaves can span 2 feet [0.6 metres]. Thick, fleshy red petioles hold the blades above the ground. The RHS describes these stalks as hollow and angular. The broad leaves give the plant a bold outline. It suits vegetable plots, cottage gardens, and informal ornamental beds.

Small flowers rise above the leaves in midsummer. They form dense panicles on upright flowering stems. Their colour ranges from yellowish white to greenish white. The reddish fruit has three wings and holds one seed. The RHS describes the later seeds as flat and tan. Remove old flower spikes unless you plan to save seed. Cut back faded leaves when the growing season ends. Plants can be raised from seed or divided.

Grow this rhubarb in sun or partial shade. It accepts chalk, clay, loam, and sandy soils. Acid, neutral, and alkaline soils all suit it. Keep the soil moist, but allow excess water to drain. Water during dry summer spells. Add a manure mulch in spring without burying the crown. The RHS rates its hardiness as H6. This covers winter lows of about −20 to −15°C under UK conditions. Slugs and aphids may attack it. Crown rot, honey fungus, and virus diseases are other possible problems.

Cooked petioles can be used in pies and purées. Do not confuse these edible stalks with the poisonous leaf blades. Leaves and roots are the main toxic parts. Eating large amounts can cause severe poisoning in people. Signs include stomach pain, mouth irritation, weakness, and vomiting. Severe cases may be fatal. Pets can also suffer poisoning after eating the leaves. Soluble oxalates can cause drooling, tremors, and kidney injury. Pet Poison Helpline distinguishes the low-oxalate stalks from the dangerous leaves.